Exploding bridgewire operated switch



March 10, 1970 J. B. MALASPINA 3,500,279

EXPLODING BRIDGEWIRE OPERATED SWITCH Filed July 26, 1968 F IG. 2

INVENTOR JOHN B; MALASP/IVA w BY gdg lv'ro wwm 3,500,279 EXPLODING BRIDGEWIRE OPERATED SWITCH John B. Malaspina, Ormond Beach, Fla., assignor to the United States of America as represented by the Secretary of the Navy Filed July 26, 1968, Ser. No. 748,073 Int. Cl. H01h 37/76 US. Cl. 337-409 6 Claims ABSTRACT OF THE DISCLOSURE An exploding bridgewire switch comprising a bridgewire covered with a non-flammable silicone grease. Upon the explosion of the bridgewire, energy is transferred to a commutator which then closes a switch contact.

STATEMENT OF GOVERNMENT INTEREST The invention defined herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to an electrical switch that is immune from the effects of hazards of electromagnetic radiation.

Description of the prior art In the field of bridgewire detonators, it had been the general practice to employ explosively actuated detonators to perform a switching function. Detonators actuated by the closing of a switch either simultaneously with an arming operation or at some time interval after an arming operation have been known to be initiated by radio or radar waves. This inadvertent actuation of the detonator has made it necessary to provide between the detonator and the missile fuel or whatever the detonator actuates, a safety in the form of a shield or movable plate which is moved to an out of the way position by the arming mechanism. The possibility of inadvertent actuation of the detonator, however, after the arming operation and before firing has made this type of installation dangerous and unreliable.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide an exploding bridgewire operated switch which embraces all the advantages of similarly employed switches and possesses none of the aforedescribed disadvantages. To attain this, the present invention contemplates a unique arrangement in the bridgewire whereby the switch itself does not employ any explosives and as such it is practically immune from the effects of hazards of electromagnetic radiation.

Therefore, an object of the present invention is the provision of a detonator which is impervious to spurious electrostatic and electromagnetic energy waves and which is easily actuated.

Another object is to provide a bridgewire switch that does not employ explosives.

A further object of the invention is the provision of a switch utilizing a coating of non-flammable silicone grease for protective purposes.

Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following description of a preferred embodiment of the invention as illustrated in the accompanying sheet of drawing.

3,500,279 Patented Mar. 10, 1970 BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal cross-sectional view of the switch in accordance with the present invention showing the contacts in a first position.

FIG. 2 is a longitudinal cross-sectional view of the switch of FIG. 1 showing the contacts in a second position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views there is disclosed in FIG. 1 an electroexplosive switch 11 that does not employ explosives. The switch is shown as a single throw, single pole, normally open device but could be a multi-pole normally open or closed device or function as both simultaneously. The switch mechanism consists mainly of conducting body 13, a main pair of electrodes 20 and 20, a bridgewire 14 connected across electrodes 20 and 20', a plastic commutator 16 connected by adhesive to the bridgewire and forming an air chamber 30, a center electrical contact 17, spring contact leaves 18 and a center electrode 19. The entire switch housing is enclosed by glass seals 21 and 22 and a plastic seal 23.

In operation, the switch is actuated by the discharge of a capacitor used in any typical firing circuit (not shown). Upon the application of the discharge pulse across leads 20 and 20', bridgewire 14 will explode. The air in air expansion chamber 30 will expand developing a shock wave which is transferred to commutator 16 by a nonfiammable silicone grease that is placed over the bridgewire. While the grease is not necessary for the desired results, it will greatly enhance the energy transfer capability of the bridge. The shock waves will break the adhesive bond holding the commutator 16 and then drive the plastic commutator assembly, consisting of center contact 17, which fastens contact leaves 18 to the commutator, as shown in FIGS. 1 and 2, towards center electrode 19 thereby closing an electrical circuit through the center electrode 19 center contact 17, contact leaves 18 and body 13. Contact leaves 18 then close and grasp around the center electrode thereby preventing the switch from reopening.

FIG. 2 is identical to FIG. 1 except that the switch is in the closed position. FIG. 2 shows contact leaves 18 grasping center electrode 19 and thereby preventing the switch from opening.

By placing a non-flammable silicone grease, such as thixotrophic grease, over the wire, the efiiciency of the switch is increased by over 200 percent. The use of the grease increases the energy in the order of 2 joules. It is to be understood, however, that the use of a grease coating is not necessary for the operation of switch 11.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An electroexplosive bridgewire switch immune to inadvertent firing comprising:

a sealed conducting outer shell containing a pair of spaced electrical contact members having free ends extending outward from said shell;

an exploding bridgewire connected across said spaced contacts wherein said bridgewire explodes upon application of electrical energy to said pair of contact members;

energy transfer means adjacent to said bridgewire;

sliding contact means responsive to said energy transfer means wherein said sliding means is movable in a 3 a direction opposite to that in which said pair of 5. The switch of claim 4 wherein said locking means electrical contact members extend; comprises conductive spring contact leaves. locking means electrically and physically connected to 6. The switch of claim 5 wherein said outer shell is said sliding contact means; and sealed by glass plugs at both ends. a center electrode to receive said sliding contact means and complete a closed electrical path from said 5 References Clted sliding contact means through said conducting outer UNITED STATES PATENTS shell by way of said locking means upon explosion 3 274 363 9/1966 McGirr et 31 337405 of Said bridgewil'e and subsequsnt engagement of 31243504 4/1966 McGirretal: III: 337 409 said locking means with said center electrode. 10 2,321,602 1/1953 Hordechuck 2. The switch of claim 1 wherein said bridgewire is 1 909 5 5 1933 Douglas 2 1 9 coated to improve the energy transfer- 769L824 9/1904 Hopkinson 337-409 3. The switch of claim 2 wherein said coating is a nomfiammable Silicone grease BERNARD A. GILHEANY, Primary Examiner 4. The switch of claim 3 wherein said energy transfer 15 DEWITT M, MORGAN, A i t t E i means comprises an air-expansion chamber and a mechanical commutator to drive said movable sliding contact means. 10228; 337-413, 414 

